Cooling system for electronic apparatus



P 1, 1954 c. J. CRESSMAN ETAL 3,147,403

COOLING SYSTEM FOR ELECTRONIC APPARATUS Filed 001,- 10, 1962 2Sheets-Sheet 1 v INVENTORS (K/4,415! J.

(WI/f Sept. 1, 1 4 c. J. CRESSMAN ETAL 3,147,403

coomuc SYSTEM FOR ELECTRONIC APPARATUS Filed Oct. 10, 1962 2Sheets-Sheet 2 .DT: u

United States Patent 3,147,403 COOLING SYSTEM FOR ELECTRONIC APPARATUSCharles J. Cressman, Hatboro, and Victor J. Malmowskl, Havertown, Pa,assignors to Philco Corporation, Philadelphia, Pa., a corporation ofDelaware Filed Oct. 10, 1962, Ser. No. 229,685 9 Claims. (Cl. 317-100)This invention relates generally to forced-air cooling systems and moreparticularly to improved means for cooling pivotally supportedelectronic apparatus.

While of broader applicability the invention will be illustrated anddescribed in connection with its use in the computer field.

With the widening demand both militarily and commercially for computerscapable of handling increasingly greater amounts of information athigher rates of speed the need for high density electronic packaging hasbecome of paramount importance. A concomitant of this trend is the needfor improved means for removing the heat generated within such compactassemblies in order to maintain system stability.

To achieve optimum use of available space while at the same timeproviding for ease of access to the unit to facilitate system servicingand maintenance use has been made of pivotally mounted electronicapparatus. One such arrangement is to use a paginated system whereinpluralities of modular assemblies are mounted on frames or pagesfoldable into a closed or tightly compacted operating position. Whenservicing is required the pages can be opened permitting easy access tocomponent parts of the system.

Because of the high density packaging made possible by thisconstructional arrangement there is a considerable problem of heatremoval. This problem is further complicated by the desirability ofcooling the pages when moved into their open position in order to permitservicing or maintenance procedures to be carried out under normaloperating conditions.

Prior art apparatus directed to the problem of cooling equipment of thistype has generally taken the form of providing a pressure plenum inwhich the air-outlet means is suiiiciently restrictive of the air flowto permit a static pressure buildup within the plenum to insure auniform air distribution over the area serviced.

This approach has the disadvantages of requiring the employment of highcapacity, large size blowers in addition to requiring the use ofenlarged, hermetically sealed plenums, factors which increase both thesize of the unit and its constructional cost. Moreover, the prior artapproach has been to use a fixed air distributing system which is onlyeffectual in cooling the page when in its normally closed operatingposition.

It is accordingly a general object of the present invention to provide asystem for cooling electronic apparatus of the type described whicheliminates the aforementioned difiiculties of the prior art.

It is another object of the invention to provide a blower systemuniquely adapted to achieve uniform cooling of paginated electronicassemblies.

It is a further and more particularized object of the invention toprovide a cooling system which has optimum compactness, is capable ofcooling paginated electronic assemblies in either their closed or openposition and provides selective cooling of the multiplicity ofcomponents comprising the assembly.

These and other objects and features of the invention will becomeapparent by reference to the following detailed description and drawingsin which:

FIGURE 1 is a perspective showing of a central processing unit of adigital computer embodying the present 3,1414%?) Patented Sept. 1, 1964ice invention, the electronic pages of the processor being shown in boththeir open and stored or packaged positions;

FIGURE 2 is a partially sectionalized side elevation of the page andcooling apparatus showing constructional details of the assembly;

FIGURE 3 is a fragmentary plan view of the processor showing pages intheir closed position; and

FIGURE 4 is a sectional elevational view taken along the cutting plane4-4 seen in FIGURE 3 showing details of the bearing duct construction.

In achievement of the aforementioned as well as other objectives, apreferred embodiment of the invention contemplates the provision of aunique air-distributing system which is transportable with theelectronic page assembly and is capable of selectively and continuouslycooling the page assembly over its entire surface and throughout itsrange of motion.

Referring to FIGURE 1, there is shown a central processing unit 10 of adigital computer, the unit comprising a control and maintenance console12, a selfcontained power supply 14 and a plurality of pages 16 eachconsisting of four pairs of horizontally disposed, serially connectedpans 18 each containing over 200 printed circuit modules, a few of whichhave been illustrated at 20. The base 21 of the unit is provided with afully enclosed chamber which contains a blower system designed forselective and individual cooling of each of the page assemblies, airbeing supplied to each page through a uniquely constructed page bearingand tapered air distributing duct or plenum 22 secured to the page formovement therewith.

Certain of the pages are shown in their open position to facilitateexplanation of their construction. Each page is defined by a metal frame24 hinged along its inner edge 26 to the cabinet structure 28. The pagesare held in closed position within the cabinet 30 by conventional latchmeans 32 and are limited in their outward movement by links 34 which arepivotally secured at one end to the upper surface of the frame crossmember 38. The opposite end of the link terminates in an upwardlypresented leg portion retained within track means 40 for slidingmovement therein. To facilitate securement of pans 18 to the page thereis provided a recessed, vertically extending ledge along frame portionsof the page which in cooperation with a medially disposed channel member42 forms a support for opposite vertical edge portions of each pan.

constructional details of the pan assemblies and their electricalinnerconnection are fully set forth in copending application Serial No.193,963, filed May 11, 1962 and assigned to the assignee of the presentinvention. Since that aspect of the computer construction forms no partof the present invention no further elaboration is believed necessary.

In the illustrated example the electronic network of the centralprocessor is contained on seven pages each containing over 1600 printedwiring modules requiring individualized cooling. In fulfilling thisrequirement each page is serviced by its own independent cooling system.The elements comprising each of the cooling systems are shown insectional elevation in FIGURE 2 and consist of a centrifugal blower 44,an air distributing plenum 22 removably secured to the bottom edge ofthe page, and an interposed transitional bearing duct 46 interconnectingthe plenum and blower in fluid flow communication.

To minimize turbulence in the translation of the air stream from thevertically directed output passage 43 of the blower 44 to thehorizontally disposed cooling plenum 22 the bearing duct 46 is equippedwith a series of armately shaped guide vanes 50. The air flow path isdiagrammatically shown by arrows in FIGURE 2 and is kept as smooth aspossible to prevent eddy currents and to reduce frictional drag on theair stream. By reducing the static pressure buildup within the systemthe size of the air-moving equipment necessary to meet the systemscooling requirements can be kept at a minimum.

To cool the page effectively requires the air being delivered by theblower to be divided into a plurality of discrete streams individualones of which are directed through the vertical running channels 52(FIGURE 2) formed by the vertically aligned columns of modules 20. Toaccomplish this the duct 22 is provided with a number of rectangularlyshaped air discharge ports 54, along its page confronting surface 55,equal in number to that of the module-formed channels 52. Thisconstruction is seen most clearly in FIGURES 2 and 3. To provide: forthe equal distribution of air in such a system the cooling plenum isconfigured to accommodate the reduced quantity of air which flows withinthe duct at the downstream side of each outlet. By reducing the ductscross sectional area the velocity of the air stream within the ductremains substantially constant. The ports are of equal size to equalizetheir outlet flow rates.

To achieve a balanced-flow system, herein defined as a system which isnot dependent on the development of a static pressure head to insureuniform air distribution, the aggregate area of the outlet vents 54 ismade substantially equal to that of the air intake area. To compensatefor the reduced quantity of flow resulting from loss of air throughsuccessive, upstream vents, the plenum is tapered. This constructionprovides for movement of air through the plenum at constant velocity aspreviously mentioned. Since the outlets are of equal area the quantityof flow through each of the vents is identical.

By this arrangement the need for a static pressure plenum is eliminatedand there is provided a balanced, air-distributing system of extremecompactness and one capable of achieving uniform air distribution.

To permit cooling of the page in both its closed and opened position,the page is supported on a rotary L- shaped casing 56 journalled in thefloor of the unit. Constructional details of this arrangement are shownin FIGURE 4.

As seen in that figure the page frame 24 is bolted to a circular plate60 welded to the casing 56, for rotation therewith. The lower portion ofthe casing terminates in a flanged collar 62 provided with a dependingjournal member 64. A bronze support bearing 66 is positioned within anopening provided in the floor of the unit and is secured thereto by boltmeans 70. Positioned between flanges 72 and 74 of the bearing andjournal members respectively, is a bronze thrust washer 76 designedrotatively to carry the full weight of the page assembly. Interposed ina connection between the fitting 82, secured to the bearing 66, and theoutlet scroll 83 of blower 44, is a flexible duct 84 desirably made oflow-temperature resistant neoprene on fiberglass fabric. The ends of theflexible duct are secured to the fitting 82 and blower 44 by means of aworm-gear clamp 86, only the upper connection being shown. By thisarrangement cooling of the page can be carried out using a blowerfixedly secured within chamber 21 without adversely affecting thecornpactness of the paginated electronic packaging.

To provide a more rigid unit the frame 88 of the central page of theprocessor, see FIGURE 3, is fixedly secured to the cabinet structure.This page remains fully accessible since the flanking pages arepivotally mounted in the manner above described.

FIGURE 3 is a plan view of the computer assembly showing pages in theirclosed position. The page im mediately adjacent the fixed frame 88 ispivotable into a position which places the leading edge 90 of itscooling plenum 22 in contiguous relation to the plenum carried by thefixed frame 88. The air cooling systems of the two pages act selectivelyand cooperably to direct streams of air upwardly through the columns 52formed by the tiers of modular printed wiring assemblies 20. The PWassemblies have only been shown in selected locations for clarity ofillustration. To permit venting of the heatladened air in its movementupward over the page the top of the unit is provided with an open metalgrid work 92.

The outermost page, as seen in FIGURE 3, acts in cooperation with thefoldable front cover 94 to form a series of partially sealed channels.In those assemblies employing an even number of pages the face-to-facearrangement previously described can be employed while in arrangementsusing uneven numbers of pages the alternative construction of using theunit covers provides an equally satisfactory arrangement for sealedoperation.

As seen in FIGURES l and 2 air is drawn into the unit by way of thelouvered opening 100 provided in the front face of the base chamber 102through an air filter 104. Air passes through this filter into the eye106 of the blower 44 and is expelled from the blower scroll 83 throughthe flexible duct 84 and vaned casing 56 into the tapered duct 22. Thepattern of air distribution achieved by this arrangement isdiagrammatically shown by arrows in FIGURE 2. As previously explainedthe quantity of air coming from each of the discharge vents 54 isidentical and results in uniform cooling of the page assembly.Furthermore, by resort to this constructional arrangement, cooling maybe maintained regardless of page position. When the page is in the openposition, such for example, as the position of the two foremost pagesshown in FIGURE 1, the air Washes out about midway up the page. Thismode of operation however is. effective in preventing overheating of thepage as a result of the turbulence created by spillage of air from andover lower surfaces of the page. Since the heat generated in the lowerhalf of the page is removed without rising over the componentspositioned at higher elevations, satisfactory operation in the openposition can be maintained in an ambient atmosphere as high as F.

To provide a better understanding of the cooling system comprising thepresent invention, each page of electronic apparatus shown in FIGURE 1is approximately 4 ft. x 4 ft. in area and contains as stated over 1600printed wiring panels. The panels in the illustrated example aresubstantially identical both in construction and in their heatgenerating capabilities, each printed wiring module generating about .2of a watt, or in the aggregate producing a heat load of over 400 wattsper page inclusive of the heat introduced into the system by the bloweritself. To facilitate cooling, the panels 20 are arranged in tiers ofvertical oriented columns to provide for unobstructed movement of airthrough panel-formed channels 52.

Given a temperature range which is not to be exceeded, such for exampleas an 8 C. rise over the temperature of the ambient atmosphere, andassuming an operating ambient temperature of 27 C. (80 F.), the quantityof air required, based on an 80% operating efliciency, can be readilycomputed. Based on the above conditions the air required to cool a pageof electronic equipment of the type described is approximately 120c.f.m. By resort to the unique constructional features described, thestatic pressure of the air distributing system cant be kept below about.45 inches of water. Given these desired performance characteristics acentrifugal blower of something less than 10 inch diameter capable ofdelivering 150 c.f.m. at a static pressure of 0" of water and c.f.m. ata static pressure of 1" of water operating on a 60 cycle single phasevolt A.C. system was found to provide satisfactory operation.

To keep noise at a minimum, and to stay within the practical limits offan power, a main duct velocity of 2000 ft./min. was selected.

The packaging arrangement shown results in the formation of 84 channelsthrough which air is to be selectively directed. To provide for auniform distribution of air through these channels the duct is taperedin the manner previously described, and provided with 84 air vents ofequal area along its length. To handle a flow rate of 130 c.f.m. at avelocity not in excess of 2000 feet per minute requires each air vent tohave an outlet area of about .117 inches To provide for most effectivecooling each air vent is centered between adjacent panels and is of awidth not exceeding panel spacing. This arrangement is best seen inFIGURE 3. To comply with these requirements the outlet size was madewide by /8" long. As mentioned before to maintain a balanced flow and toprevent restriction of the air stream, the inlet and outlet areas aremade substantially equal. Given an inside height dimension of 4" and awidth of 2 /2 at the inlet side 108 of the duct, the duct is uniformlytapered throughout its length of 34 inches to a height of about /2" inthe tip area. The minimal height of the duct in the tip area must besomething less than a feather edge to avoid excessive frictional lossesin the downstream end of the duct. There is a critical ratio of ductperimetric surface to cross-sectional area below which it is notdesirable to go if losses are to be kept at a minimum. This criticalratio is empirically determined and in the illustrated example was foundto occur in ducts having a rectangular cross section of a dimension lessthan approximately /2 inch by 2 inches.

A unit employing the air cooling system described, when in thecompletely sealed condition experiences a temperature rise of somethingless than 7 C. which is well within the assumed design requirements.

The central fixed page of the unit, which carries the memory-controlcircuits, has a heat output which is three times greater than that ofthe other pages. Because of the fixed nature of this page it is servicedby a rigidly mounted blower 110 which is of substantially greater sizethan those needed for cooling the other pages. The balance of the airdistributing system which serves this page is the same as that alreadydescribed with the exception that no transitional bearing duct isrequired. To aid in disassembling the system and in repairing the ductit is detachably secured to the page by metal screws not shown and tothe rotary casing by means of duct clamps 112.

In summary, there is provided an air distributing system of extremecompactness and one which is particularly adapted for use with paginatedelectronic apparatus and which is elfective in providing a uniformdistribution of air over the entire surface undergoing treatment.Moreover, this uniform distribution of air is achieved without resort topreviously required high-pressure plenums and their attendantdisadvantagessuch as providing an airtight duct-and by a uniquecombination of features is made available to pivotable electronicassemblies using fixed, air-moving equipment.

Although the invention has been described with particular reference tospecific practice and embodiments, it will be understood by thoseskilled in the art that the apparatus of the invention may be changedand modified without materially affecting the invention as defined inthe appended claims.

We claim:

I. A forced-air cooling system for use with a pivotable page ofelectronic apparatus of the type described, comprising: arir-movingmeans; an air discharge plenum constructed and arranged for pivotalmovement with said page; and aper-tured bearing means supportive of saidpage assembly and interposed in a connection permitting pivotal movementbetween said air-moving means and plenum and providing an aircommunicating passageway therebetween.

2. A forced-air cooling system for use with a pivotable page ofelectronic apparatus of the type described, comprising: air-movingmeans; an elongate discharge plenum mounted for movement with said pageand containing a series of discharge vents along a surface thereof andsaid plenum having a configuration producing a substantially uniformdischarge of air from each of said vents; and

a P g means interposed in a connection between said air-moving means andsaid plenum permitting their relative movement and providing anair-communicating passageway therebetween.

3. A forced-air cooling system for use with a pivotable page ofelectronic apparatus of the type described, comprising: fixedair-lmoving means; a multiported air-discharge plenum mounted forpivotal movement with said and apertured bearing means supportive ofsaid page assembly interconnected in air-conducting relation betweensaid air-moving means and plenum and constructed and arranged to permitrelative movement therebetween.

4. A forced-air cooling system for use with a pivotable page ofelectronic apparatus of the type described, comprising: air movingmeans; an air-discharge plenum mounted for pivotal movement with saidpage and having a plurality of air discharge vents of equal sizeprovided along its length adapted to direct individual streams of airover said apparatus, and said plenum being configured to provide auniform distribution of air from each of said vents; and aperturedbearing means supportive of said page assembly interposed in aconnection permitting pivotal movement between said air-moving means andplenum and providing an air-communicating passageway therebetween.

5. Forced-air cooling apparatus for use with a pivotable electronic pageassembly of the type described, comprising: air-moving means; an airdischarge plenum mounted for pivotal movement with said page assemblyand having a plurality of discharge vents of substantially equal sizealong one surface thereof adapted to deliver streams of air over saidpage assembly, and said plenum being tapered in the direction of airflow to provide uniform discharge of air from each of said vents; andbearing means supportive of said page assembly and interposed in pivotalconnection between said air-moving means and duct and constructed toprovide an air communicating passageway therebetween.

6. The combination comprising: a pivotable page of components arrangedin channel-forming tiers; air-moving means; duct means secured to saidpage for pivotal movement therewith having a plurality of equal-sizevents disposed along a page-confronting surface thereof adapted todeliver individual streams of air through said tierformed channels; andmeans supportive of said page assembly pivotaily interconnecting saidair moving means and duct means in air fiow communication.

7. A forced-air cooling system for use with a pivotable page ofelectronic apparatus of the type described, comprising: air-movingmeans; an elongate discharge duct movable with said page and containinga series of dis charge vents adapted to deliver individual streams ofair over said apparatus and said duct having a tapered configurationproducing a substantially uniform discharge of air from each of saidvents; and means interposed in connection between said air-moving meansand said duct permitting their relative movement and providing anaircommunicating passageway therebetween.

8. The combination comprising: a pair of pages of electronic apparatus,of the type described, at least one of which is pivotable intosubstantially closed, confronting relation with the other of said pages,each containing components arranged in aligned channel-forming tiers;elongate duct means secured to an edge portion of each of said pages formovement therewith and said duct means having a plurality ofsubstantially equal-size vents disposed along a surface thereof adaptedto deliver individual streams of air over its associated page assemblyand said ducts having a configuration providing for substantiallyuniform discharge of air from each of said vents; air-moving meansassociated with said duct means; apertured bearing means supportive ofsaid pivotable page assembly interposed in a connection permittingpivotal movement between said air-moving means and duct and providing anair-communicating passageway therebetween; and said pages when in closedposition forming, through cooperative alignment of confrontingcomponents on each of said pages, a plurality of discrete channels, andsaid ducts abutting to form a composite airdischarge .system of alignedpairs of air vents for delivery of confluent streams of air throughindividual ones of said channels.

9. The combination comprising: a pair of page assemblies of electronicapparatus, of the type described, at least one of which is pivotableinto substantially closed confronting relation with the other of saidpage assemblies, and each containing components arranged verticallyaligned; elongate duct means mounted for movement with each of said pageassemblies and having a plurality of substantially equalasize ventsdisposed along its length for delivery of individual streams of air overits associated page assembly, said duct means further having a taperedconfiguration providing for substantially uniform discharge of air fromeach of said vents; airmoving means associated with said duct means;means interposed in a connection between said air-moving means and ductmeans permitting their relative movement and providing anair-communicating passageway therehetween; and said page assemblies inclosed position forming, through cooperative alignment of confirontingcomponents on each of said pages, a plurality of discrete,vertically-running channels and said ducts forming a compositeair-discharge system of aligned pairs of air vents for delivery ofconfluent streams of air through individual ones of said channels.

References Cited in the file of this patent UNITED STATES PATENTS3,120,166 Lyman Feb. 4, 1964

1. A FORCED-AIR COOLING SYSTEM FOR USE WITH A PIVOTABLE PAGE OFELECTRONIC APPARATUS OF THE TYPE DESCRIBED, COMPRISING: AIR-MOVINGMEANS; AN AIR DISCHARGE PLENUM CONSTRUCTED AND ARRANGED FOR PIVOTALMOVEMENT WITH SAID PAGE; AND APERTURED BEARING MEANS SUPPORTIVE OF SAIDPAGE ASSEMBLY AND INTERPOSED IN A CONNECTION PERMITTING PIVOTAL MOVEMENTBETWEEN SAID AIR-MOVING MEANS AND PLENUM AND PROVIDING AN AIRCOMMUNICATING PASSAGEWAY THEREBETWEEN.